My major
research program over the last two decades has been the sensory basis
of long-distance orientation and navigation. These studies have been
conducted both in field situations (Ithaca and Arizona) and in the
laboratory (Mudd Hall and Liddell Field Station), depending upon
the nature of the questions. Most of our work has focused on amphibians
and reptiles as model systems, since these organisms are often locally
abundant and easy to manipulate, but we have also conducted experiments
with humans. We were the first to discover that amphibians and reptiles
can detect and use skylight polarization patterns for orientation
(polarotaxis) and that the critical receptors for this cue are extraocular
(pineal and related structures). We were also first to show that
amphibians can detect and use the earth's magnetic field for orientation,
although the critical receptor remains unknown. Other studies have
dealt with the influence of slope on orientation, the ability to
learn a new homesite, the importance of individual variability, time-dependent
orientation mechanisms, the role of environmental stress in orientation,
and the function of melatonin in re-setting internal clocks which
are then used for orientation. Recently, we were able to demonstrate
for the first time that amphibians are capable of true navigation.
Most of these studies are conducted using the red-spotted newt, an
abundant species in the Ithaca area that has both aquatic and terrestrial
life stages. Our studies on human orientation have dealt primarily
with tests for the possible use of magnetic cues, which we failed
to find despite an earlier claim. Recently, I have initiated a comparative
study of electroreception in salamanders. In addition to these studies
on behavior, I have also been involved in studies on the evolution
and systematics of amphibians and reptiles. Most of this work is
centered on the herpetofaunas of China and Central America.